Pulsed magnetic release mechanism

Abstract

An electromagnetic release apparatus and method are provided for unfastening a magnetically actuated surveillance marker clip assembly from an article. The release apparatus includes a primary solenoid coil that, when energized, produces a magnetic field of sufficient force to initially unlock the clip assembly for removal. A secondary magnet produces another magnetic field sufficient in force to retain the clip assembly in the unlocked position. The secondary magnet is mounted to a piston slidably received in the central bore of the primary solenoid coil. The primary solenoid coil is energized by inserting the clip assembly into the central bore of the coil, thereby, pressing the piston downwardly until it closes a "one-shot" microswitch. The electrical charge of a capacitor is then discharged through the primary coil to produce the relatively high power magnetic field for unlocking the clip assembly. A clip assembly removal reminder system assures proper processing of an article and removal of the clip assembly by the clerk or cashier. The system includes an interrogation and detection circuit for detecting the presence of a clip assembly at a final checkout station. An alarm remains continuously activated until the clip assembly is removed from the final checkout station and the release apparatus is activated to remove the clip assembly from the article.

We claim: 
     
       1. An electromagnetic release apparatus for removing a surveillance marker of the like from an article wherein said marker includes a magnetically actuated locking mechanism for fastening the marker to the article, comprising: primary electromagnet means for producing a first, strong magnetic field of sufficient force to open said marker locking mechanism;   secondary magnet means for producing a second magnetic field of lesser strength than said first magnetic field but having sufficient force to retain said marker locking mechanism in an open position once opened by said primary electromagnet means;   actuating means for energizing said primary electromagnet means to provide said first magnetic field; and   means for deactivating said primary electromagnet means within a preselected period of time following energization thereof to substantially eliminate overheating and overloading of said primary electromagnet means during marker removal from an article.   
     
     
       2. The electromagnetic release apparatus set forth in claim 1, wherein said primary electromagnet means is in the form of a solenoid coil having a central bore. 
     
     
       3. The electromagnetic release apparatus set forth in claim 2, wherein piston means are slidably received in said central bore of said primary solenoid coil. 
     
     
       4. The electromagnetic release apparatus set forth in claim 3, wherein means are provided for biasing said piston means to a rest position. 
     
     
       5. The electromagnetic release apparatus set forth in claim 4, wherein said piston means includes a head section supporting said secondary magnet means. 
     
     
       6. The electromagnetic release apparatus set forth in claim 5, wherein said piston means includes a distal end opposite said head section and switch means are provided for actuating said primary coil; said distal end of said piston means activating said switch means to actuate said primary coil when said head section of said piston means is pushed down by inserting said marker into said central bore. 
     
     
       7. The electromagnetic release apparatus set forth in claim 6, wherein a substantially cylindrical support member is provided, said primary coil being concentrically disposed around said support member and said support member serving to define said central bore for slidably receiving said piston means. 
     
     
       8. The electromagnetic release apparatus set forth in claim 7, wherein said support member is mounted on a base member housing said switch means. 
     
     
       9. The electromagnetic release apparatus set forth in claim 8, wherein said support member includes an upper wall opposite said base member for maintaining said head section of said piston means within said central bore when in said rest position, said upper wall including an aperture overlying said secondary magnet means for the receipt of said marker. 
     
     
       10. The electromagnetic release apparatus set forth in claim 1, wherein circuit means are provided for pulsed operation of said primary electromagnet means so as to substantially eliminate overheating. 
     
     
       11. The electromagnetic release apparatus set forth in claim 10, wherein said circuit means is a pulsed capacitor discharge circuit. 
     
     
       12. The electromagnetic release apparatus set forth in claim 1, wherein said secondary magnet means is a permanent magnet. 
     
     
       13. The electromagnetic release apparatus set forth in claim 1, wherein said apparatus further includes marker removal reminder means for substantially eliminating false alarms from properly purchased articles improperly processed by a cashier. 
     
     
       14. The electromagnetic release apparatus set forth in claim 13, wherein said marker removal reminder means includes interrogation and detection means for determining the presence of a marker at a final checkout station and means for indicating to a cashier that a marker is fastened to the article. 
     
     
       15. The electromagnetic release apparatus set forth in claim 14, wherein said interrogation and detection means includes control circuitry and a mat containing both interrogation and detection coils, said mat being positioned adjacent a cashier counter at a final checkout station where the cashier handles the articles being purchased. 
     
     
       16. The electromagnetic release apparatus set forth in claim 14, wherein means are provided for continuously indicating the presence of a marker on the article being purchased until such time as the release apparatus is actuated to remove the marker from the article. 
     
     
       17. The electromagnetic release apparatus set forth in claim 16, wherein said indicating means is a light. 
     
     
       18. The electromagnetic release apparatus set forth in claim 16, said indicating means is a horn. 
     
     
       19. A method of removing a surveillance marker of the like from an article, wherein said marker includes a magnetically actuated locking mechanism for fastening the marker to the article, comprising the steps of: energizing a primary electromagnet to produce a first, strong magnetic field sufficient in force to open said marker locking mechanism;   applying a second magnetic field from a secondary magnet to said marker locking mechanism, said second magnetic field being of lesser strength than said first magnetic field but having a force sufficient to maintain said marker locking mechanism in an open position once opened by energizing said primary electromagnet; and   deactivating said primary electromagnet within a preselected period of time following energization thereof to substantially eliminate overheating and overloading of said primary electromagnet during marker removal from an article.   
     
     
       20. The method set forth in claim 19, wherein said energizing step includes the step of pulsing the electromagnet. 
     
     
       21. The method set forth in claim 19, including the additional step of indicating the presence of a marker attached to an article at a final checkout station until said energizing step is initiated to remove the marker from the article.